Changing Compression Ratio & Gear Ratio

adheesh · 1st October 2007, 22:40

Hi. I wanted to know if there is any (cost effective) way to change :
1. The compression ratio of an engine
2. Gear ratio of a car.

amitpunjani · 1st October 2007, 23:19

The cheapest way to increase the compression ratio is by installing an another head gasket or else you could go overbore the cylinder liners. This would require complete overhaul of the engine.

flipsyde · 2nd October 2007, 00:15

Quote:

Originally Posted by amitpunjani

The cheapest way to increase the compression ratio is by installing an another head gasket or else you could go overbore the cylinder liners. This would require complete overhaul of the engine.

its not clear whether he wants to increase or decrease his compression ratio. installing another head gasket would only decrease the compression ratio.

shaving the head would effectively increase the compression ratio.

wats all this for anyway?

mclaren1885 · 2nd October 2007, 00:21

To increase CR of engine.

1. Shave head.
2. Use high CR pistons.
3. Use longer conrods.
4. Use a thinner head gasket.

To change gear ratios you have to change the gears with different ratios

.

greatmana2000 · 2nd October 2007, 11:54

To increase compression get a higher deck piston , and to lower get a lower deck piston .

adheesh · 2nd October 2007, 13:08

Thanx for the quick response. I would like to increase the compression ratio fRom 7.1:1 to about 9:1. Can it be done just by changing the header gasket ? Also would the changing of gear ratios require the replacement of whole gear box or just some off the gears?

ananthkamath · 3rd October 2007, 00:15

7.1:1 hmmm...is this a Fiat we are talking about? If yes then shaving the head is the way to go. Yes, it is the most cost effective way.

mclaren1885 · 3rd October 2007, 09:54

Quote:

Originally Posted by adheesh

Thanx for the quick response. I would like to increase the compression ratio fRom 7.1:1 to about 9:1. Can it be done just by changing the header gasket ? Also would the changing of gear ratios require the replacement of whole gear box or just some off the gears?

Shaving the head as ananth has mentioned. If you can give the dimensions of the pistons maybe someone might be able to recommend some high comp pistons as well.

Changing of gear ratios would include changing of some gears & if need be the final drive and not the entire gearbox.

1st October 2007, 22:40	#1
adheesh BHPian Join Date: May 2007 Location: Bombay Posts: 526 Thanked: 53 Times View My Garage	Changing Compression Ratio & Gear Ratio Hi. I wanted to know if there is any (cost effective) way to change : 1. The compression ratio of an engine 2. Gear ratio of a car.
	() Thanks

1st October 2007, 23:19	#2
amitpunjani BHPian Join Date: Jul 2007 Location: Delhi Posts: 451 Thanked: 109 Times	compression ratio The cheapest way to increase the compression ratio is by installing an another head gasket or else you could go overbore the cylinder liners. This would require complete overhaul of the engine.
	() Thanks

2nd October 2007, 00:21	#4
mclaren1885 BANNED Join Date: Jul 2005 Location: Bangalore (the city of modded cars) !! Posts: 4,820 Thanked: 45 Times View My Garage Infractions: 0/1 (10)	To increase CR of engine. 1. Shave head. 2. Use high CR pistons. 3. Use longer conrods. 4. Use a thinner head gasket. To change gear ratios you have to change the gears with different ratios .
	() Thanks

2nd October 2007, 11:54	#5
greatmana2000 BANNED Join Date: Apr 2006 Location: chennai Posts: 703 Thanked: 58 Times	To increase compression get a higher deck piston , and to lower get a lower deck piston .
	() Thanks

2nd October 2007, 13:08	#6
adheesh BHPian Join Date: May 2007 Location: Bombay Posts: 526 Thanked: 53 Times View My Garage	Thanx for the quick response. I would like to increase the compression ratio fRom 7.1:1 to about 9:1. Can it be done just by changing the header gasket ? Also would the changing of gear ratios require the replacement of whole gear box or just some off the gears?
	() Thanks

3rd October 2007, 00:15	#7
ananthkamath Senior - BHPian Join Date: Jul 2005 Location: Mangalore Posts: 1,209 Thanked: 80 Times View My Garage	7.1:1 hmmm...is this a Fiat we are talking about? If yes then shaving the head is the way to go. Yes, it is the most cost effective way.
	() Thanks